Atomic positions displaced. Electron diffraction : challenges for structure analysis ⦠electron diffraction data can b
IDENTIFICATION – FINGERPRINTING – SOLVING ab-intio NANOSTRUCTURES BY
PRECESSION ELECTRON DIFFRACTION
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PRECESSION ELECTRON DIFFRACTION NEW analysis technique > 25 articles in 2 years !
Ultramicroscopy Special Issue vol.107 issue 6-7 June 2007
Unknown nanostructures…… HOW analyze them ??
Single crystal > 5 microns X-ray diffraction
Powder X-ray diffraction
TEM microscopy
X- Ray powder diffraction: limitations < 10nm
overlapping
> 1Pm
Nanocrystals : peak broadening
Electron diffraction: advantages Every TEM (electron microscope) may produce ED patterns from individual single nanocrystals
TEM goniometer
ED information: Cell parameter and symmetry determination Measuring intensity values leads to structure determination
Electron diffraction : challenges for structure analysis … electron diffraction data can be strongly distorted by dynamical scattering
Dynamical scattering ( thickness > 10 nm )˫
WRONG MODEL light atoms do not appear Atomic positions displaced
Kinematical scattering (very thin crystals)˫
I (k) = I F (k) I 2 CORRECT MODEL
Solution: Precession Electron Diffraction (Vincent-Midgley)˫ . before precession NO precession Beam precesses about exact zone axis direction; reduces extent of dynamical scattering in on-axis condition.
PRECESSION REFLECTIONS MORE KINEMATICAL ( LIKE X-RAY CASE)
WITH precession
Precession AFTER n of ctio Proje t beam en Incid
Vincent & Midgley Ultramicroscopy 53 (1994) 271, 306
J. Gjønnes et al. Acta Cryst A54 (1998)
Advantages of precession in single exposure data collection
with beam precession, Ewald sphere also precess though the reciprocal space
• More fully recorded reflections • More spots per image • Reduced dynamic effect
SPINNING STAR UNIVERSAL INTERFASE FOR PRECESSION ELECTRON DIFFRACTION FOR ANY TEM
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JEOL 200 kv,JEOL 120 KV,2010,2100, 2000, 2010 FEG
¥
FEI Tecnai 30 FEG , Tecnai 12 (120 kv),Tecnai 20 ( 200 kv)˫ , Tecnai 10
¥
Philips EMXXX, CM10, CM20, CM30 , STWIN, UTWIN
Topcon 200 KV (Japan demo facility) ¥
¥
Can be easily installed to any TEM 100- 400 KV (LaB6-FEG)˫ ¥
Zeiss 912 ˫ Hitachi 200 KV
¥Precession is possible for a parallel or convergent beam
¥
Precession spot size ( 5 - 50 nm )˫
Precession angle can vary continuously from 0° to 4°, to observe true crystallographic symmetry variation ¥
Ab-initio structure solution with precession of …… Catalysts ( zeolites)˫ Oxides ( perovskites )˫ Complex oxides (Cs-Nb-O )˫ Minerals Polymers Pharmaceuticals …… Proteins
APPLICATION : FIND TRUE CRYSTAL SYMMETRY – SOLVING CRYSTAL STRUCTURES
[100]
PRECESSION OFF
Garnet cubic Ia3d a=1.2 nm
[100] IDEAL KINEMATICAL
simulation
PRECESSION ON
UVAROVITE Ca3Cr2(SiO4)3
Dynamical interactions due to thickness effects may deform intensities in a way that crystal symmetry cannot be recognized; by applying precession true crystal symmetry can be revealed and dynamical scattering is greatly reduced PRECESSION ED INTENSITIES (PED ) ARE CLOSE TO ( IDEAL ) KINEMATICAL INTENSITIES : WE CAN USE PED TO SOLVE DIRECTLY CRYSTAL STRUCTURES OF NANOCRYSTALS LIKE IN XRAY DIFFRACTION Courtesy M.Gemmi Univ of Milano
Is possible from simple ZOLZ/FOLZ symmetry comparison to deduce
point and space group nanocrystal symmetry
J.P.Mornirolli, JW Steeds Ultramicroscopy 1992, 45 , 219
HOW ?
by simply increasing precession angle , FOLZ /ZOLZ reflections and their relative symmetry becomes visible in ED patterns
PRECESSION OFF
FOLZ
FOLZ
ZOLZ ZOLZ
D D q q
ZOLZ
D q
SiC FOLZ
Space group deterrmination by
reflections
ZOLZ
PRECESSION ELECTRON DIFFRACTION SiC 4H hexagonal
P63mc
Courtesy JP Mornirolli Univ of Lille France
reflections
D q
AUTOMATIC crystal symmetry determination by analysis of ZOLZ @ FOLZ precession patterns
hk1
Precession electron diffraction : ab initio determination of nanostructures TEM crystal experiment
ED intensities collection from several zone axis (ELD – Triple )˫ semi- automatic (off-line)˫
STRUCTURE DETERMINATION (Direct methods)˫ semi-automatic (SIR software)˫ Refinement crystal structure
Electron diffraction intensities are measured automatically ( ELD software )
FROM Image plates Photo film OR CCD camera
1k x 1k 2k x 2k 4k x 4k
8k x 8k
or from electron diffractometer
3D structure solution examples Mauro Gemmi and Stavros Nicolopoulos Structure solution with three-dimensional sets of precessed electron diffraction intensities
Ultramicroscopy, Volume 107, Issues 6-7, June-July 2007, Pages 483-494
Åkermanite
Uvarovite
Structure
Composition
Space Group
Åkermanite Uvarovite
(Ca2MgSi2O7) P-421m Ca3(Al0.4Cr0.6)2Si3O12 I a –3 d
Cations Oxygens 3 3
3 1
Structure solution with precession diffraction: Åkermanite Three-dimensional set of precession electron diffraction intensities obtained merging [1 0 0] [0 0 1] [1 0 1] [1 0 2] zone axes. All atoms found, correctly labelled, = 0.1262 from published coordinates. Atom Ca Si Mg O O O
X(Sir) 0.843 0.648 0.500 0.654 0.567 0.500
Y(Sir) 0.343 0.148 0.500 0.154 0.330 0.000
Z(Sir) 0.486 0.060 0.000 0.801 0.211 0.193
X(Pub) 0.832 0.640 0.000 0.860 0.581 0.000
Y(Pub) 0.332 0.140 0.000 0.640 0.314 0.500
Z(Pub) 0.494 0.065 0.000 0.256 0.217 0.817
Distance 0.12498 0.09056 0.00000 0.32573 0.16526 0.05064
PRECESSION RESOLUTION - X RAY RESOLUTION SYNCHROTRON X RAY
0.12 nm CONVENTIONAL X- RAY
0.05 nm
> 17.000
REFLECTIONS OBSERVED
0.19 nm UTWIN
0.24 nm STWIN
TVIPS F224 HD
Weirich et al Ultramicroscopy 2006 Cs-Nb-W-0 oxide , ALL heavy atoms revealed by precession diffraction
PRECESSION OFF
PRECESSION ON
simulation
PRECESSION on POLYMERS Melon ([C6N7(NH2)(NH)]n, plane group p2gg a = 16.7 Å, b = 12.4 Å, g = 90°, Z = 4
Courtesy M. Doblinger Univ of Munich Germany
Precession from pharmaceutical nanocrystals
PED patterns in pharmaceutical crystals allow to work with close or with ZA oriented patterns , revealing true crystal symmetry and kinematical intensities good for structure determinations
amoxycillin penicillin G-potassium 0.9Å
1.1Å
1.1 Å
without precession
without precession
Samples C.Giacovazzo CNR Bari
with precession
Courtesy JP Abrahams, D.Georguieva Univ Leiden
Precession ED from 3d protein lysozyme nanocrystals
protein crystals show much better quality PED patterns ( suitable for symmetry and structure determination ) than conventional SAED patterns
2.7Å 2.7Å
Courtesy JP Abrahams, D.Georguieva Univ Leiden
ZEOLITES ITQ-29 ab initio structure determination
no PRECESION
with PRECESION
Is possible to determine complete structure from a single ED obtained at 100 kV
Different methods: direct methods (FOCUS), maximun entropy (MICE), real space (FOX), ...
Zeolita A
Ihkl proportional to |Fhkl|2 Pm3m, a=11.87Å
ZEOLITES : Ab initio determination of MCM-22 (ITQ-1) zeolite framework
PRECESSION ON
IDEAL KINEMATICAL
3D frameworks can be revealed by collecting and combining quasikinematical precession electron diffraction intensities from different zone axis to one 3D electron diffraction data set ( image courtesy Douglas Dorset USA)˫
PRECESSION ON
old TEM…… works well !
SOLUTION: ENHANCE NEW TEM
> 36 installations world-wide OR UPGRADE OLDER TEM TO POWERFUL STRUCTURE DETERMINATION
NanoMEGAS INSTALLATIONS WORLDWIDE PHILIPS TEM CM30 , CM 20 , CM12, CM10 , EM 400 JEOL TEM JEOL 2000, JEOL 2100, JEOL 2010, JEOL 2010 FEG , JEOL 1400 FEI TEM TECNAI 10, TECNAI 12, TECNAI 20 , TECNAI 20 FEG STEM, TEM 30 FEG STEM ZEISS TEM 912 OMEGA FILTER
DEMO SITES PARIS Philips CM12 JAPAN Tokyo Topcon EM 002B 200 kv
TVIPS Munich JEOL 2010, Tecnai12
TOTAL > 36 INSTALLATIONS
1st precession electron diffraction user meeting
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